I can not figure mission 3, the first Vikings mission, out. I am losing a lot of troops and not gaining ground. I got the bottom third of the main area clear when the Dark Tribe over whelmed my towers and turn the ground black. How do I beat this mission?

The trick to facing the Dark Tribe is to only recruit Bowmen. Swordsmen and Axemen will get shredded at close range, so don't bother with them. Once you get three or more groups of 100 Bowmen (preferably Level 2 or higher), you can try engaging the Dark Tribe. You'll want to bring 20+ Gardeners, too, and your Bowmen should protect them at all costs. Focus on reclaiming the burial grounds, as destroying all the Mushroom Farms (and, hence, the Dark Temple) might not be possible in this mission. The white-ish flames around the Dark Temple will wipe out your soldiers in droves, so beware!